What is the pH of Rain?

The pH of rain is typically slightly acidic, ranging from approximately 5.0 to 5.6. This is due to the presence of carbon dioxide in the atmosphere, which dissolves in rainwater to form carbonic acid.

Factors Affecting Rainwater pH

Several factors influence the precise pH of rainwater:

• Carbon Dioxide: The primary contributor to the natural acidity of rain. When CO2 dissolves, it forms carbonic acid, resulting in a pH around 5.6. (Reference: Multiple sources including EPA & NH DES fact sheets)

• Pollution: Air pollutants like sulfur dioxide and nitrogen oxides can significantly lower the pH, creating acid rain with pH values as low as 4.2 to 4.4. (Reference: US EPA - What is Acid Rain?)

• Location: The pH of rain can vary geographically based on pollution levels and other atmospheric conditions. Rural areas tend to have less polluted rain with a higher pH than urban or industrial regions. (Reference: Multiple sources showing varying pH levels measured)

• Measurement Method: The accuracy of pH measurement depends on the method and equipment used. Discrepancies in reported pH values might result from different testing procedures or instrument limitations. (Reference: Reddit discussion highlighting potential measurement inaccuracies)

Normal vs. Acid Rain pH Levels

Here's a summary comparing pH levels:

It's crucial to remember that the pH of rainwater is a dynamic value influenced by many factors. The figures presented represent typical ranges, not absolute constants.